Quantum Efficiency Enhancement in Si Avalanche Photodiodes in the NIR Regime via Surface Texturing Towards Autonomous Driving Applications

Light detection and ranging (LiDAR) has been implemented in autonomous driving vehicles, but the current technology suffers from low photon detection efficiency. This paper reports a Silvaco TCAD simulation study on Si PIN avalanche photodiodes with micro surface structures and anti-reflective coating at 905 nm and 940 nm near infrared regime. Via varying the micro surface structure, anti-reflective coating thickness and intrinsic layer depth, optimized quantum efficiencies of 77.8% and 62.9% are obtained for the 905 nm and 940 nm wavelengths respectively. These results are >22% and >26% larger than for their flat counterparts. We also investigate the influence of light source angles on the quantum efficiency of different surface structures and demonstrate that efficiency is only weakly degraded by non-optimal incidence angles. This means that device performance should be robust even in poor weather conditions with significant light diffusion.